1. Field of the Invention
The present invention relates to an SOR exposure system which uses synchrotron radiation light from an SOR ring and, more particularly, to an SOR exposure system for transferring patterns on masks onto semiconductor wafers used in the field of manufacturing semiconductor devices.
2. Description of the Related Art
The use of synchrotron radiation (hereinafter referred to as SOR radiation) as a light source for X-ray exposure has been proposed. A method has been considered in which a sheet-like beam of SOR radiation is expanded perpendicular to the plane of the beam using a mirror, and an exposure region is thereby created. In this method, as disclosed in Japanese Patent Laid-Open No. 2-98121, the damage to mirrors caused by X-rays is reduced by providing, in addition to an exposure adjustment shutter for controlling exposure time, a mirror-protective shutter for shielding X-rays disposed in a portion of the radiation path nearer to the X-ray source than the mirror, and the opening/closing of this shutter is controlled.
There has been a problem in that, in addition to X-rays, radiation rays such as .alpha. particles, .beta. particles, .gamma. rays, or neutrons, all of which are harmful to the human body, are generated when electrons are implanted into an SOR ring and when the SOR ring stops. As shown in FIG. 11, a method to shield these radiation rays has been proposed in which an SOR ring 1 and an exposure apparatus 2 are placed in separate chambers and a partition 6 is formed into a radiation-ray shielding wall made of, for example, concrete.
However, although the partition 6 has a duct 18 through which X-rays 3 are permitted to pass, no measures have been taken against leakage of radiation rays from the duct 18. These radiation rays are transmitted through a mirror-protective shutter provided to shield X-rays, causing damage to the mirror.